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Advanced Placement Calculus AB Evaluation David Klein Professor of Mathematics California State University, Northridge Fall 2007 Documents reviewed: • Calculus: Calculus AB Calculus BC Course Description, The College Entrance Examination Board, 2005 • Teacher’s Guide: AP Calculus, The College Entrance Examination Board and Educational Testing Service, 1997 • 2003 AP Calculus AB and AP Calculus BC, Released Exams, The College Entrance Examination Board, 2005 • 1998 AP Calculus AB and AP Calculus BC, Released Exams, The College Entrance Examination Board and Educational Testing Service, 1999 • AP Calculus AB Free Response Questions, AP Calculus AB Free Response Items, Form B, AP Calculus AB Scoring Guidelines, AP Calculus AB Scoring Guidelines, Form B for the years 2004, 2005, 2006 • Four sample syllabi of Calculus AB classroom teachers provided by The College Board Background There are two AP Calculus courses, Calculus AB and Calculus BC. The College Board recommends that both be taught as a college-level courses. Calculus AB is intended to correspond to 2/3 of a year long college calculus sequence, and Calculus BC is intended to substitute for a full year of college calculus. There are separate exams for each of these courses, but the grade for the BC exam includes a subscore based on the portion of the exam devoted to Calculus AB topics, approximately 60% of the test. By design the overlapping topics are not covered in any greater depth than on the AB exam. According to the College Board, the reliability of the Calculus AB subscore is nearly equal to the reliabilities of the Calculus AB and BC exams. The focus of this report is on Calculus AB, and the grades are for Calculus AB only. However, some discussion of Calculus BC is also included because of the overlap of topics, and to set a broader context for the first course. The AP Calculus exams are graded on a five point scale: AP Grade Qualification 5 Extremely well qualified 4 Well qualified 3 Qualified 2 Possibly Qualified 1 No recommendation The duration of each AB and BC Calculus examination is 3 hours and 15 minutes. Section I of each exam consists of multiple choice questions, and Section II consists of free response questions. The two sections receive equal weight in the grading, and each of the two sections is further divided into a Part A and a Part B. Part A of Section I has 28 multiple choice questions to be completed in 55 minutes, and does not allow students to use calculators. Part B of Section I requires a graphing calculator and consists of 17 questions to be completed in 50 minutes. Each of Parts A and B of Section II lasts 45 minutes and each consist of 3 free response problems. Calculators are allowed only for Part A. During the time allotted for Part B, students may continue to work on Part A questions, but without a calculator. Not all of the questions in the parts of the test that allow calculators necessarily require their use, but some do. Each college and university sets its own AP credit and placement policies, but many institutions offer at least a semester of credit for high grades on the AB exam, and a year of credit for high scores on the BC exam. The Teacher's Guide explains the philosophy, themes, and goals of the AP Calculus courses: "Calculus AB and Calculus BC are primarily concerned with developing the students' understanding of concepts of calculus, and providing experience with its methods and applications. The courses emphasize a multirepresentational approach to calculus, with concepts, results, and problems being expressed geometrically, numerically, analytically, and verbally." Working with functions geometrically, numerically, analytically, and verbally, and understanding the interconnections is the first listed goal of AP Calculus. It is referred to as "the rule of four," which the Teacher's Guide describes as a "rallying cry for the calculus reform movement," in contrast to "the earlier paradigm of doing almost everything analytically." Technology plays a central role in AP Calculus. One of the listed goals is "the incorporation of technology into the course." The Guide recommends that "students should be comfortable using machines to solve problems, experiment, interpret results, and verify conclusions," and further explains that, "The most natural way to achieve this goal is to let the students use their own technology at all times, except perhaps for certain targeted 'no-calculator' assessments (which should be rare, and never at the exploratory phase of student learning)." The Teacher's Guide presents AP Calculus as an extension of the K-12 mathematics reform movement led by the National Council of Teachers of Mathematics or NCTM, as explained in this passage: "Teachers familiar with the NCTM Standards and/or with various education reform documents will recognize many of these goals as being part of a broader blueprint for educational change. Adopting them for our students has necessitated (for many of us) a change in the way we teach, and for the AP Calculus Committee the Standards have suggested some significant changes in what we will teach in the immediate future." Content The AP Calculus curriculum has noteworthy strengths. One is the emphasis on the definite integral as a limit of Riemann sums to counter the tendency of students to think of integrals only as anti-derivatives. The explicit inclusion of the Mean Value Theorem along with geometric consequences (for both AB and BC) is also commendable, due to its theoretical importance in calculus. Also of value for students who will apply calculus to scientific and engineering problems is a focus on correct units to answers to word problems, and an emphasis within the curriculum on verbal descriptions of mathematical concepts using correct terminology. The value of this emphasis is two-fold: it helps students to understand the meanings of word problems and therefore is a first step to problem-solving, and it helps students communicate their solutions to others. There are also deficiencies and controversial features in the AP Calculus program. Among them are the following. 1) Calculators vs. Analytic Methods Of the categories of the "rule of four," analytic methods receive the least emphasis in the Teacher's Guide. The topic, "Computation of derivatives," which calls for the ability to compute derivatives of standard functions, along with knowledge of the chain rule, and the rules for finding derivatives of sums, differences, products, and quotients of functions, comes at the end of the list of topics. The Guide explains, "Perhaps the most significant thing about this topic [computation of derivatives] is that it is listed last, consistent with the philosophy that the emphasis of the course is not on manipulation." To that end, the Guide explains, "Logarithmic differentiation is no longer on the list of topics." This is a mismatch with mainstream university calculus courses, where this is a standard topic. Practice with logarithmic differentiation helps to develop technical fluency in computations involving logarithms and exponentials, and it should be included in the curriculum. The AP Calculus exams require the use of graphing calculators that can at minimum graph functions within an arbitrary viewing window, numerically calculate derivatives and definite integrals, and find roots of functions. The exams also allow calculators with Computer Algebra Systems (CAS) that can symbolically calculate limits, derivatives, and integrals. For the sake of equity, however, the exam questions are purposefully crafted in such a way so as to avoid giving advantage to examinees with these more powerful machines. For example, students are asked only to find definite integrals with numerical answers, and not indefinite integrals, in those parts of the AB and BC exams that allow calculators. In this way calculators with CAS provide no direct advantage over what the other allowed calculators can do. Here and elsewhere, technology determines mathematical content, a negative feature. One of the topics in the AB and BC courses is the Trapezoidal Rule for numerical integration. This is a standard topic in first year calculus courses. However, Simpson's Rule, also a standard topic, is not included in the AP Calculus curriculum because, the Teacher's Guide explains, "it was viewed by most students as just another formula to memorize...(The Trapezoidal Rule is also a formula, but more students can see exactly where it comes from)." Ironically, in Appendix 3, the Teacher's Guide provides graphing calculator programs for Simpson's Rule that students are invited to enter into their calculators if they do not already come equipped with one. Students are permitted to use these programs during the AP Exams, thus adding to the "black box" role played by the calculator. As described above, fluency in hand calculations receives relatively low emphasis in the AP Calculus curriculum, by design, and that choice is reflected by the exams. Only the simplest paper and pencil calculations involving algebra and calculus are required on the AP Calculus exams. This curricular choice is flawed. Technical fluency in hand calculations is essential for following – or producing – some mathematical proofs, and for the purpose of deriving scientific formulae in the mathematical sciences. The Calculus Committee of the College Board was aware of the controversial nature of this de- emphasis. The Teacher's Guide includes the following passage: "A final concern about calculators is the unfortunate fact that not all teachers at the college level approve of their use. It is therefore quite possible that an AP student will do well in your course, become comfortable with technology, and then enter a college mathematics course in which no calculators are allowed." The Guide nevertheless gives overly optimistic assurances of the appropriateness of the AP Calculus curriculum.
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